Overview
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ABSTRACT
The internal sulphate reaction due to Delayed Formation of Ettringite (DEF) is an expansive reaction of concrete that can severely damage structures.
The article has 3 parts:
- the first one presents the physico-chemical mechanisms of RSI, the influence of various parameters and the mechanical consequences;
- the second presents the visible disorders in the structures, the diagnosis, monitoring, evaluation and management of the structures;
- the third introduces the French IFSTTAR recommendations to prevent disorders; these are based on a crossing between the category of risk of occurrence of disorders on a given structure and its exposure class, this crossing making it possible to define a level of prevention which then determines the precautions to be applied which are essentially based on the limitation of the maximum temperature reached at the heart of the structures and on the choice of an appropriate concrete composition.
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Read the articleAUTHORS
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Bruno GODART: Former Deputy Director of the Materials & Structures Department at Gustave Eiffel University - Honorary Chairman, French Civil Engineering Association
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Loïc DIVET: Doctorate in materials science - Former Director of the Physicochemical Behavior and Durability of Materials Laboratory at Gustave Eiffel University
INTRODUCTION
Internal sulfate reaction (ISR) through the delayed formation of ettringite is a cause of disorders that can severely damage concrete structures.
The first cases appeared abroad, from 1987 onwards, in certain prefabricated parts that had been subjected to heat treatment inappropriate to the formulation and exposure of the concrete (e.g. railroad sleepers).
Since 1997, this phenomenon has been observed in France on bridges where the concrete had been poured in place. These were mainly massive structures (piers, headers on piers or abutments, etc.) in contact with water or subject to high humidity. Then, it was observed on bridges whose girders were prefabricated in a factory and subjected to heat treatment.
Unlike more conventional sulfate reactions, where sulfates attack the concrete from the outside, causing progressive degradation from the surface to the core, RSI affects the entire concrete without the need for an external source of sulfates. The result is swelling of the material and cracking of the structure.
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KEYWORDS
building | damage | pathology | concrete | Delayed Formation of Ettringite (DEF) | ettringite
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Internal sulfate reaction in concrete structures
Mechanism of the internal sulfate reaction
Bibliography
- (1) - HORNAIN (H.), ROUGEAU (P.) - Dégradations du béton liées à l'action des sulfates et aux phénomènes d'alcali-réaction – - Dans Grandeurs associées à la Durabilité des Bétons sous la direction de G. Arliguie et H. Hornain, Presses de l'École Nationale des Ponts et Chaussées, pp. 205-262 (2007).
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Standards and norms
- Cement testing methods – Part 1: Determination of resistances. - NF EN 196-1 -
- Cement testing methods – Part 9: Hydration heat – Semi-adiabatic method. - NF EN 196-9 -
- Cement – Part 1: Composition, specifications and conformity criteria for common cements. - NF EN 197-1 -
- Concrete – Specification, performance, production and compliance. – National supplement to standard NF EN 206+A2. - NF EN...
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AFGC – Association française de Génie civil
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CEREMA – Centre d'études et d'expertise sur les risques, l'environnement, la mobilité et l'aménagement (Center for studies and expertise on risks, the environment,...
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